Commonly, melt flow in an injection molding machine is controlled by a valve pin, which is moved in a melt passage by an actuating mechanism. Depending on the layout constraints of the melt passages and other components in an injection molding machine, it can be desirable to provide an actuating mechanism for a valve pin in a melt channel, that extends laterally to the valve pin.
The technical literature shows several hot runner injection nozzle designs having a valve pin actuating mechanism incorporating a lateral arm, or linkage, that directly engages a valve pin to push the valve pin towards a mold gate to stop the transfer of molten material from the nozzle into the mold cavity. Reference is made in this regard to U.S. Pat. No. 3,806,295, U.S. Pat. No. 4,026,518, U.S. Pat. No. 4,222,733 and U.S. Pat. No. 4,272,236. In these patents, however, the lateral arm does not engage the valve pin in order to move it back to an ‘open’ position. Rather, the movement of the valve pin away from the mold gate is achieved by the back pressure generated by the pressurized melt in the nozzle. In these designs the valve pin is not attached to any guiding sleeve movable inside the nozzle. A typical example of this lateral valve gating approach is shown in FIG. 9, which shows a mechanism disclosed in U.S. Pat. No. 4,272,236.
The technical literature further shows hot runner injection nozzles where the valve pin is engaged laterally by an arm, or linkage. This design makes possible to actuate the valve pin inside the nozzle in both directions relative to the mold gate. Reference is made in this regard to U.S. Pat. No. 3,488,810, U.S. Pat. No. 4,712,995 and U.S. Pat. No. 4,793,795 where the lateral arm, or linkage has circular movement with respect to the valve pin. In these designs the valve pin is engaged directly by the linkage, and is not attached to a guiding sleeve movable inside the nozzle. A typical example of this lateral valve gating approach is shown in FIG. 10, which shows a mechanism disclosed in U.S. Pat. No. 4,712,995.
The technical literature further shows hot runner injection nozzles where the valve pin is engaged laterally by an arm, or linkage. Reference is made in this regard to U.S. Pat. No. 4,919,606, U.S. Pat. No. 5,902,614, U.S. Pat. No. 5,948,450 and U.S. Pat. No. 5,984,661. In these designs, the valve pin is attached to a guiding sleeve movable inside the nozzle, and the lateral arm, or linkage, has a circular movement with respect to the valve pin. Typical examples of this lateral valve gating approach are shown in FIGS. 11, 12a and 12b, which show mechanisms disclosed in U.S. Pat. No. 4,919,606 and U.S. Pat. No. 5,948,450 respectively. In the more recent U.S. Pat. No. 5,948,450, the lateral arm does not directly engage the guiding sleeve, (also referred to as a sled). As shown in FIGS. 12a and 12b, the actuating mechanism of the '450 patent includes a lateral arm that engages a pin, which is, in turn, connected to the sled. Furthermore, the pin is retained in place by an additional spring. The mechanism disclosed in the '450 patent includes many parts, which inherently increases its complexity and cost of production and which can reduce its reliability. It is known that, due to the high temperature of operation, which can be, for example, in the range of 250° C., and due to the huge frequency of injection cycles, which can be, for example, in the range of 400 movements/minute, it is desirable to have a minimum number of parts involved in the actuation of the valve pin.
There is a continuing need for a laterally actuated valve gating mechanism that is reliable in operation, that provides reduced stresses on the valve pin and is made of a reduced number of components.